One of the shortcomings of xerographic ground planes based on evaporated metal film is that the metal film can be converted to its oxide with xerographic cycling. Ground plane materials such as Al, Ti, Zr are electrochemically active and can be oxidized to metal oxides easily. Holes traversing the photoreceptor in combination with ambient water electrochemically can convert the metals to their optically transparent and insulating oxides resulting in a change in charge acceptance and transparency. Long print runs of a single image can lead to variations in optical transparency corresponding to image content. Consequently, both erase illumination (for photoreceptor belts) and ground plane conductivity can vary spatially according to image content leading to image ghosts which can limit photoreceptor belt life. Suitable materials for non-electrochemically reactive optically transparent conductive ground planes are limited. Dispersed carbon particles are non-electrochemically reactive but they are unsuitable because of the poor optical transparency of dispersed carbon films. Alternative optically transparent conductive ground planes formed of, for example, cuprous iodide and conducting polymers including polypyrrole and polyaniline also have issues of reproducibility and cost as well as the relative immaturity of the technology. Ground planes formed of sputtered indium tin oxide (ITO) have problems due to electrical cycling because the indium can migrate with DC current flow. As a result, small insulating areas develop in the ground plane that turn into photoreceptor print defects. Hence, there is a need for improved ground planes.
Furthermore, one of the shortcomings of the image on image (IOI) approach to color xerography is the absorption of some of the illumination used to write the xerographic image by the previously applied toner layers. The amount of yellow, cyan, and black deposited by a specific laser exposure depends on the amount of magenta previously applied. The amount of cyan applied depends on the pervious magenta and yellow toner layer thickness levels. This issue with IOI can be eliminated by exposing the photoreceptor from the inside of the belt module through the back of the belt. However, cost effective illumination is difficult with the existing photoreceptors which only transmits about 10% of the incident illumination.
Accordingly, there is a need for developing transparent ground planes that are non-oxidizable and stable against temperature and humidity variations.